Investigation of Coatings, Corrosion and Wear Characteristics of Machined Biomaterials through Hydroxyapatite Mixed-EDM Process: A Review

Abstract

Together, 316L steel, magnesium-alloy, Ni-Ti, titanium-alloy, and cobalt-alloy are commonly employed biomaterials for biomedical applications due to their excellent mechanical characteristics and resistance to corrosion, even though at times they can be incompatible with the body. This is attributed to their poor biofunction, whereby they tend to release contaminants from their attenuated surfaces. Coating of the surface is therefore required to mitigate the release of contaminants. The coating of biomaterials can be achieved through either physical or chemical deposition techniques. However, a newly developed manufacturing process, known as powder mixed-electro discharge machining (PM-EDM), is enabling these biomaterials to be concurrently machined and coated. Thermoelectrical processes allow the migration and removal of the materials from the machined surface caused by melting and chemical reactions during the machining. Hydroxyapatite powder (HAp), yielding Ca, P, and O, is widely used to form biocompatible coatings. The HAp added-EDM process has been reported to significantly improve the coating properties, corrosion, and wear resistance, and biofunctions of biomaterials. This article extensively explores the current development of bio-coatings and the wear and corrosion characteristics of biomaterials through the HAp mixed-EDM process, including the importance of these for biomaterial performance. This review presents a comparative analysis of machined surface properties using the existing deposition methods and the EDM technique employing HAp. The dominance of the process factors over the performance is discussed thoroughly. This study also discusses challenges and areas for future research.

A comprehensive review on metallic implant biomaterials and their subtractive manufacturing

“…Bains et al [ 280 ] performed nano-HAp powder–mixed EDM (PM-EDM) on Ti alloy surface for producing HAp bio-coatings, for which the wear and corrosion rates were also hampered. However, as Al-Amin et al [ 296 ] discussed, powder mixing still poses challenges in obtaining uniform thickness, proper adhesion, and controlling HAp phase transformation, which must be solved before the widespread use of this method for orthopedic implants. As further explained by Al-Amin et al [ 297 ], the more significant weight of HAp particles and its polar nature produces a heterogeneous mixture with dielectric oil impairs Ca-P ions deposition's regularity.…”

A review on β-Ti alloys for biomedical applications: The influence of alloy composition and thermomechanical processing on mechanical properties, phase composition, and microstructure

“…The most important factors that affect the implant's corrosion resistance are dissolved oxygen, chlorides, and the pH value of the biofluids. 54 The passive oxide layer thickness on the implant material and the chemical composition of the implant material has a significant impact on implant biocompatibility. 55 As the implants are exposed to a high level of humidity and a high level of local corrosion in the bio-environment, the implant's lower corrosion resistance in biofluids results in toxic ions release, which further causes toxic reactions in the body.…”

Evaluation of the Biocompatibility and Osteogenic Properties of Metal Oxide Coatings Applied by Magnetron Sputtering as Potential Biofunctional Surface Modifications for Orthopedic Implants

“…Coatings thickness can be correlated to corrosion rates and coating adhesion strength, which are desirable characteristics in an in vivo system. Generally, the thinner the coating, the greater its adhesion strength to the substrate, and the poorer its corrosion protection [ 86 ]. In addition, detachment of the coatings might cause the accumulation of debris in the surrounding tissue and consequently cause inflammation and exacerbate immunological responses [ 32 ].…”